Assessment of critical habitat for common snapping turtles (Chelydra serpentina) in an urbanized coastal wetland

Abstract

Critical habitats such as nesting areas and overwintering sites are specific areas used by organisms to carry out important life functions. In many urbanized centers, critical habitats of at-risk species have often become degraded and/or fragmented because of human activities. Such is the case for the population of common snapping turtles (Chelydra serpentina) in Cootes Paradise Marsh, a highly urbanized ecosystem located at the western tip of Lake Ontario. In addition to these threats, mortality from collisions with cars on a four-lane highway at the western end of the marsh has greatly reduced wildlife populations. Here, we examine long-term changes in critical habitat distribution that has accompanied urbanization of Cootes Paradise Marsh from 1934 to 2010. We delineated potential nesting habitat for snapping turtles in 7 digitized aerial photos, using literature information and 2017 nesting surveys as guides. Between 1934 and 2010, total area of potential nesting habitat decreased by almost 50%. Nesting surveys confirmed that snapping turtles were disproportionately using created nesting mounds and this suggests that availability of natural nesting habitat is limited. We also radio tracked 11 snapping turtles to identify use of overwintering habitat. Temperature loggers monitored in-situ water temperatures at each turtle’s location and other unconfirmed habitats. The snapping turtle population overwintered in a wide range of upland terrestrial habitats and we found consistent characteristics regarding water temperature across both confirmed and unconfirmed sites, therefore suggesting overwintering habitat may not be limiting within the marsh.

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Acknowledgements

All field work was conducted respectful of approved McMaster University animal use protocols (No. 17-01-05) and site-specific permits (Hamilton Conservation Authority land access, Wildlife Scientific Collector’s Authorization No. 1084392 and Royal Botanical Gardens No. 2016-07). Thank you to the students of the Chow-Fraser lab and to Jacqueline Garnett for assisting with data collection. Thanks to Dylan Melmer for his insight and help with analysis. We also like to thank the Hamilton Conservation Authority and Royal Botanical Gardens.

Funding

This project was funded by the Natural Sciences and Engineering Research Council of Canada.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical approval

This article does not contain any studies with human participants or animals performed by any of the authors.

Brooks RJ, Brown GP, Gailbrait DA (1991) Effects of a sudden increase in natural mortality of adults on a population of the common snapping turtle (Chelydra serpentina). Can J Zool 69:1314–1320CrossRefGoogle Scholar

Brown GP, Brooks RJ (1994) Characteristics of and fidelity to hibernacula in a northern population of snapping turtles Chelydra serpentina. Copeia 1994:222–226CrossRefGoogle Scholar

City of Hamilton, Information Technology Services, GIS Services (2002)Digital orthoimagery of the City of Hamilton. Spring 2002. Accessed as a web map tile serviceGoogle Scholar

Committee on the Status of Endangered Wildlife in Canada [COSEWIC] (2008) COSEWIC assessment and update status report on the snapping turtle Chelydra serpentina in Canada. Committee on the status of endangered wildlife in Canada, Ottawa, CanadaGoogle Scholar

Paterson JE, Steinberg BD, Litzgus JD (2013) Not just any old pile of dirt: evaluating the use of artificial nesting mounds as conservation tools for freshwater turtles. Oryx 47(4):607–615CrossRefGoogle Scholar